Acute and chronic experimental optic neuritis. Alteration in the blood-optic nerve barrier
J. Guy and N. A. Rao
Horseradish peroxidase (HRP) tracer studies in experimental allergic optic
neuritis showed alterations in the blood-optic nerve barrier. Light and
electron microscopic examination of the optic disc disclosed intense
leakage of HRP at the lamina scleralis, with extracellular staining of both
axonal and glial columns, despite the lack of inflammation at this region.
The intraorbital optic nerve showed leakage of HRP at the sites of both
acute and chronic demyelination. Ultrastructurally, leakage of HRP was
confined to the perivascular and extracellular spaces. The mechanism of
leakage seems to be by diffusion through the endothelial cell junctions or
vesicular transport across the endothelial cells. The high predilection for
involvement of the optic nerve in chronic demyelinating disorders may be
due to the inherent weakness of the blood-brain barrier at the optic nerve
head.
